In a conventional X-ray diagnostic apparatus, as disclosed in Japanese Unexamined Patent Publication No. 2000-33083, “X-ray image forming apparatus”, data for correction is calculated from the outputs of a detector derived from an area where X-ray beams do not impinge, which area is referred to as a dark area within the detection areas of a two-dimensional semiconductive X-ray detector, and data for correction of an area where X-ray beams do impinge (hereinafter referred to as the “effective area”) are generated by using the data for correction calculated from the detector outputs derived from the dark area.
However, it has been found that noise might enter even in pixels disposed in the dark area. In this case, the data for correction generated in the dark area may be mixed with noise even when such noise is not mixed in the data obtained in the effective area. Therefore, there are problems in that the image data of one line may have an offset in gain relative to an adjacent line, to thereby generate line noise in a diagnostic image.